THE MILK GLANDS 13 



Some cells are seen that have a distinct amoeboid 

 movement; these are leucocytes that have wandered 

 through the epithelium into the glandular pockets and 

 have taken up some globules of fat. Besides these, 

 there are to be found some epithelial cells that have 

 undergone more or less degeneration. 



The chemical examination of colostrum shows its 

 principal constituents to be: water, proteids (especially 

 globulin and albumin, and also casein and nuclein com- 

 pounds), sugar, fats and cholesterin, and, besides these, 

 lecithin, various salts and other substances in smaller 

 quantities. Colostrum differs from normal milk in its 

 higher percentage of solids and especially in its higher 

 content of globulin, albumin, nuclein compounds and 

 lecithin. The chemical composition of colostrum differs 

 slightly among animals of different species. In the 

 course of a few days, the secretion of colostrum passes 

 into milk secretion so that at the expiration of about 

 one week, the secretion possesses the characteristic ap- 

 pearance and composition of milk. 



The microscopic picture of milk is quite different 

 from that described above. A very large number of 

 fat droplets (milk globules, Fig. 4) of varying sizes, and 

 a small number of more or less degenerated cells (colos- 

 trum bodies, gland cells) are distributed uniformly in 

 a transparent fluid, the milk plasma. 



It was formerly thought that milk secretion differed 

 in important particulars from other secretions in that, 

 it was considered, it occurred through partial destruc- 

 tion of the gland cells. It was supposed that during 

 secretion the cells became longer and swollen, that the 

 nucleus receded to the base of the cell while the part 

 pointing toward the cavity of the alveolus became filled 

 with numerous small fat globules. It was thought that 

 after this " fatty degeneration " reached a certain 



